With reference to FIG. 1, high-speed product inspection and cutting systems 2 that include an inspection station 3 for detecting defects in a specimen product 4 and a cutting station 5 for removing the defects are in widespread use in, for example, the processed food industry. In such a system 2, a conveyor belt 6 carries previously inspected product 4 material, such as elongated potato strips, carrots, or green beans, in a direction 7 generally orthogonal to the axis of rotation of a cutting wheel assembly 10, which is mounted overhead the conveyor belt 6.
The cutting wheel assembly 10, in response to commands delivered from an inspection station 3, selectively deploys certain cutter knives 12 radially outwardly through slots in a knife guide 14 to excise defective regions from the product 4 as it appears directly below the cutting wheel assembly 10. Having cut the product 4, the selected knives 12 retract into their respective knife support ring slots 16 until the knives 12 are again deployed. A prior art knife 12 of a type that can be used in a typical cutting wheel assembly 10 is described in detail in U.S. Pat. No. 5,029,504 of Wilbur et al. A prior art cutting wheel assembly 10 into which the prior art knife fits is described below with reference to FIGS. 2A and 2B.
With reference to FIGS. 1 and 2, a typical inspection and cutting system employs a rotating cutting wheel assembly 10 that carries multiple plastic cutter knives 12 angularly spaced around the periphery of a knife support ring or knife guide 14. Each knife guide 14 has, positioned back-to-back and around its periphery, two rings of slots 16 each of which holds a cutter knife 12. Each ring of slots 16 of the knife guide 14 fits over a different stationary cam track structure 18 and imparts rotational motion to the cutter knives 12 so that they slide along the cam track structure 18 in either one of its inner or outer annular tracks 22 and 24, respectively.
A tang 26 extends from an elongated shank 28 of each cutter knife 12 and is sized to fit in and slide between the inner and outer annular tracks 22 and 24. The inner annular track 22 receives the tangs 26 of the cutter knives 12 whenever they are in a retracted noncutting position 32, and the outer annular track 24 receives the tangs 26 whenever they are in an extended cutting position 34. A knife gate mechanism 36 guides tangs 26 into the track specified by the inspection station.
The axis of rotation 38 of the knife guide 14 is coincident with the center point 40 of the annular tracks 22 and 24. Each one of the slots 16 holds and guides a cutter knife 12 as it moves radially between the retracted noncutting position 32 and the extended cutting position 34. The recessed nature of side walls 42 of the shank 28 allows a liquid lubricant to flow between the cutter knife 12 and the sides of the slots 16 to reduce the friction forces between them.
Shifting the cutter knives 12 from one track to the other causes the cutter knives to move through a interference zone or transition 44 between the inner and outer annular tracks 22 and 24. Although transition 44 is tapered to minimize its profile, the tangs 26 ride against the sidewalls of transition 44 and exhibit wear. If the wear becomes excessive, a tang 26 may be worn down or broken off so that a cutter knife 12 is no longer held in the cutting wheel assembly 10. The loose cutter knife 12 then falls or is thrown into the product flow.
Although tang breakage is infrequent, a broken cutter knife 12 is a contaminant that must be removed before the inspected product is shipped. Such broken cutter knives 12 are, however, difficult to automatically detect and remove from the product, especially because they are typically made of plastic. The conventional method for removing broken cutter knives 12 relies on a person to watch the product flow and physically remove them.